Solution #3....Make a rule!! Follow this:
http://forums.dlink.com/index.php?topic=14959.0
Solutions 1&2. Not really enough info, no log data etc.
So, generally, do not use auto channel selection...lock onto your own channel using InSSIDer software to find the best prospects.
If your workstation is far from the router, read up on the ways to increase signal. If your workstation is close to the router, reduce transmission power in Advanced Wireless as signal may be distorted. Read many other threads on the subject regarding devices, phones, etc.